DEFECT IDENTIFICATION IN SEMICONDUCTORS BY BREWSTER-ANGLE SPECTROSCOPY

The sensitivity of the pseudo Brewster angle phi(B) and the reflectivity for p-polarized light at this angle R(p)\phi(B) to small changes in absorption is used for the identification of deep and shallow defects in semiconductors. Brewster angle spectroscopy (BAS) was performed on undoped and n-type GaAs as well as on undoped and p-type InP. Comparison with literature values shows that BAS can be used to identify deep defects at room temperature without electrical contacting. The changes in the spectra of undoped and doped GaAs and InP can be explained by involving the respective donor and acceptor levels in the transition processes. For CuInS2 the defects are analyzed by measuring R(p) close to phi(B) as a function of photon energy. The findings can be explained on the basis of existing photoluminescence data, postulating two additional deep levels at hv=E(upsilon)+0.350 eV and hv=E(upsilon)+O.625 eV. The comparison of model spectra for shallow defects with phi(B) spectra of CuInS2 grown with sulphur excess leads to identification of a level at E(upsilon)+0.015 eV in accordance with luminescence data on the energetic position of sulphur interstitials. The applicability of BAS is shown, taking into account the experimental limitation through depolarization and angle divergence.